Integrated circuit device and fabrication using metal-doped chalcogenide materials

ABSTRACT

Methods of forming metal-doped chalcogenide layers and devices containing such doped chalcogenide layers include using a plasma to induce diffusion of metal into a chalcogenide layer concurrently with metal deposition. The plasma contains at least one noble gas of low atomic weight, such as neon or helium. The plasma has a sputter yield sufficient to sputter a metal target and a UV component of its emitted spectrum sufficient to induce diffusion of the sputtered metal into the chalcogenide layer. Using such methods, a conductive layer can be formed on the doped chalcogenide layer in situ. In integrated circuit devices, such as non-volatile chalcogenide memory devices, doping of the chalcogenide layer concurrently with metal deposition and formation of a conductive layer in situ with the doping of the chalcogenide layer reduces contamination concerns and physical damage resulting from moving the device substrate from tool to tool, thus facilitating improved device reliability.

TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates generally to integrated circuitmemory devices, and in particular to the metal doping of chalcogenidematerials in the fabrication of chalcogenide memory elements andintegrated circuit devices containing such memory elements.

BACKGROUND OF THE INVENTION

[0002] Electrically programmable and erasable materials, i.e., materialsthat can be electrically switched between a generally resistive stateand a generally conductive state are well known in the art. Chalcogenidematerials are one class of examples of such materials finding use in thesemiconductor industry, particularly in the fabrication of non-volatilememory devices.

[0003] Chalcogenide materials are compounds made of one or morechalcogens and one or more elements that are more electropositive thanthe chalcogens. Chalcogens are the Group VIB elements of the traditionalIUPAC version of the periodic table, i.e., oxygen (O), sulfur (S),selenium (Se), tellurium (Te) and polonium (Po). The moreelectropositive elements are generally selected from Groups IVB and VB.Typical combinations for non-volatile memory devices include seleniumand/or tellurium with germanium (Ge) and/or antimony (Sb). However,other combinations are also known, such as combinations of arsenic (As)and sulfur.

[0004] To obtain the desired electrical characteristics, chalcogenidematerials are often doped with metal, such as copper (Cu), silver (Ag),gold (Au) or aluminum (Al). FIGS. 1A-1D depict the fabrication of asimple chalcogenide memory element 100. The basic structure of achalcogenide memory element includes a first electrode, a secondelectrode and a chalcogenide material interposed between the first andsecond electrodes. Additional detail of chalcogenide memory devices, aswell as examples of variations on the basic structure of a chalcogenidememory element, are given in U.S. Pat. No. 5,998,244 issued Dec. 7, 1999to Wolstenholme et al., U.S. Pat. No. 5,920,788 issued Jul. 6, 1999 toReinberg, and U.S. Pat. No. 5,837,564 issued Nov. 17, 1998 to Sandhu etal., each of which is commonly assigned with the assignee of the presentdisclosure. In general, chalcogenide memory elements are formed on asemiconductor wafer or other substrate as a portion of an integratedcircuit device.

[0005] Chalcogenide memory elements typically store a single bit, e.g.,a low resistivity (high conductivity) corresponding to a first logicstate and a high resistivity (low conductivity) corresponding to asecond logic state. Differing levels of resistivity of the chalcogenidememory elements are sensed using current sensing techniques well knownin the art while applying a read potential of less than the thresholdpotential.

[0006] Chalcogenide memory elements can be electrically switched betweenconductivity states by applying varying electrical fields to the dopedchalcogenide material. By applying a programming potential above somethreshold potential, the metal dopant atoms are believed to align in adendritic structure, thereby forming conductive channels and decreasingthe resistivity of the chalcogenide material. This transition isreversible by applying a potential having an opposite polarity. A rangeof applied potentials having a magnitude of less than the thresholdpotential, i.e., read potentials, can be applied without altering theresistivity of the doped chalcogenide materials. These read potentialscan be applied to the chalcogenide memory elements for sensing theresistivity of the doped chalcogenide material and, thus, the memoryelements' data values.

[0007] Unlike dynamic random access memory (DRAM) devices, anon-volatile memory device does not require a periodic refresh tomaintain its programmed state. Instead, non-volatile memory devices canbe disconnected from a power source for extended periods of time, oftenmeasured in years, without the loss of the information stored in itsmemory cells. Chalcogenide materials best suited for use in non-volatilememory devices will thus tend to maintain their degree of resistivityindefinitely if an applied voltage does not exceed the thresholdpotential.

[0008] In FIG. 1A, a first electrode 110 is formed and a chalcogenidelayer 115 is formed overlying the first electrode 110. As notedpreviously, electrical characteristics of chalcogenide layer 115 may beimproved through doping of the chalcogenide material with metal. This istypically carried out through a process known as photo-doping wherediffusion of metal atoms is photon induced. In this process, a metallayer 120 is first formed on the chalcogenide layer 115 as shown in FIG.1A. The metal layer 120 typically contains the copper, silver, gold,aluminum or other high-diffusing metal. Formation of the first electrode110 and/or the metal layer 120 is typically performed in a vacuumchamber, e.g., using a vacuum sputtering process.

[0009] To continue the photo-doping process in FIG. 1B, electromagneticradiation 125 is directed at the metal layer 120, resulting in diffusionof metal atoms from the metal layer 120 into the chalcogenide layer 115.The electromagnetic radiation 125 is generally ultraviolet (UV) light.Driving metal atoms into the chalcogenide layer 115 results in a dopedchalcogenide layer 130 containing the chalcogenide material and thediffused metal. The semiconductor wafer must generally be removed fromthe vacuum chamber to expose the wafer surface to the UV light source.

[0010] The photo-doping process is generally carried out until the metallayer 120 is completely diffused into the doped chalcogenide layer 130as shown in FIG. 1C. The thickness of the metal layer 120 should bechosen such that the desired doping level can be attained in the dopedchalcogenide layer 130. However, the metal layer 120 must be thinenough, e.g., hundreds of angstroms, to allow transmission of theelectromagnetic radiation 125 in order to produce the desiredphoton-induced diffusion of metal. As shown in FIG. 1D, a secondelectrode 150 is then formed overlying the doped chalcogenide layer 130and any remaining portion of the metal layer 120 to produce chalcogenidememory element 100. As with the first electrode 110 and/or thechalcogenide layer 115, formation of the second electrode 150 is alsotypically performed in a vacuum chamber. The second electrode 150 ispreferably a material having a different work function (φ_(m)) than thefirst electrode 110. The work function is a measure of the energyrequired to remove an electron from a material's surface.

[0011] There are several disadvantages to the traditional photo-dopingprocess. The process can be time consuming as the semiconductor wafersare moved in and out of a vacuum chamber during the various processingstages described above. This movement of the semiconductor wafers amongvarious process equipment also increases the chance of contamination orother damage during transport. Also, because the metal layer must bethin for efficient photon-induced diffusion of metal, the desired dopinglevel may not be efficiently attainable with a single photo-dopingprocess as the necessary thickness of the metal layer may result inexcessive reflection of the electromagnetic radiation.

[0012] For the reasons stated above, and for other reasons stated belowthat will become apparent to those skilled in the art upon reading andunderstanding the present specification, there is a need in the art foralternative methods for producing chalcogenide memory elements.

SUMMARY

[0013] Methods are described herein for forming metal-doped chalcogenidelayers and devices containing such doped chalcogenide layers. Themethods include using a plasma to induce diffusion of metal into achalcogenide layer concurrently with metal deposition. The plasmacontains at least one noble gas of low atomic weight, such as neon orhelium. The plasma has a sputter yield sufficient to sputter a metaltarget and a UV component of its emitted spectrum sufficient to inducediffusion of the sputtered metal into the chalcogenide layer. Using suchmethods, a conductive layer can be formed on the doped chalcogenidelayer in situ. In integrated circuit devices, such as non-volatilechalcogenide memory devices, doping of a chalcogenide layer concurrentlywith metal deposition and formation of a conductive layer in situ withthe doping of the chalcogenide layer reduces contamination concerns andphysical damage resulting from moving the device substrate from tool totool, thus facilitating improved device reliability.

[0014] For another embodiment, the invention provides a method offorming a doped chalcogenide layer. The method includes sputtering metalusing a plasma containing at least one component gas selected from thegroup consisting of neon and helium and driving the sputtered metal intoa layer of chalcogenide material using the UV component generated by theplasma.

[0015] For a further embodiment, the invention provides a method offorming a doped chalcogenide layer. The method includes forming a layerof chalcogenide material and sputtering metal onto the layer ofchalcogenide material using a plasma containing at least two noblegases. The plasma emits a spectrum having a UV component capable ofdriving the sputtered metal into the layer of chalcogenide materialthrough UV-enhanced diffusion. For one embodiment, the composition ofthe plasma is chosen to have an average atomic weight sufficient toproduce a desired sputtering efficiency. For another embodiment, thecomposition of the plasma is chosen to have a desired relative intensityof a UV component of the emitted spectrum of the plasma. For yet anotherembodiment, the composition of the plasma is chosen to have a desiredemitted spectrum of the plasma.

[0016] For one embodiment, the invention provides a method of forming achalcogenide memory element having a first electrode, a secondelectrode, and a doped chalcogenide layer interposed between the firstelectrode and the second electrode. The method includes forming achalcogenide layer on the first electrode, sputtering metal onto thechalcogenide layer and diffusing metal into the chalcogenide layer usinga first plasma containing at least one component gas selected from thegroup consisting of neon and helium, thereby forming the dopedchalcogenide layer, and sputtering metal onto the chalcogenide layerusing a second plasma containing at least one component gas having anatomic weight higher than an atomic weight of neon, thereby forming thesecond electrode. For a further embodiment, the first plasma and thesecond plasma are the same plasma. For a still further embodiment, thecomposition of the first plasma is modified to generate the secondplasma. Such modification of the composition may occur as a step changebetween sputtering stages or it may occur concurrently with sputteringof the metal.

[0017] For another embodiment, the invention provides a method offorming a chalcogenide memory element having a first electrode, a secondelectrode, and a doped chalcogenide layer interposed between the firstelectrode and the second electrode. The method includes forming achalcogenide layer on the first electrode, sputtering silver onto thechalcogenide layer and diffusing silver into the chalcogenide layerusing a first plasma generated from feed gas consisting essentially ofneon, thereby forming the doped chalcogenide layer, and sputteringsilver onto the doped chalcogenide layer using a second plasma generatedfrom feed gas consisting essentially of argon, thereby forming thesecond electrode.

[0018] For yet another embodiment, the invention provides a method offorming a non-volatile memory device. The method includes forming wordlines and forming first electrodes coupled to the word lines, whereineach word line is coupled to more than one first electrode. The methodfurther includes forming a chalcogenide layer on each first electrodeand sputtering metal onto each chalcogenide layer and diffusing metalinto each chalcogenide layer using a first plasma containing at leastone component gas selected from the group consisting of neon and helium,thereby forming doped chalcogenide layers. The method still furtherincludes sputtering metal onto each doped chalcogenide layer using asecond, different, plasma, thereby forming second electrodes. The secondplasma may contain at least one component gas having an atomic weighthigher than the atomic weight of neon. Alternatively or additionally,the second plasma may contain nitrogen (N₂) such that the secondelectrode is formed of a metal-nitride material. The method stillfurther includes forming bit lines coupled to the second electrodes,wherein each bit line is coupled to more than one second electrode. Eachdiode may be formed interposed between a second electrode and a bitline, such that each second electrode is coupled to a bit line through adiode. Alternatively, each diode may be formed interposed between afirst electrode and a word line, such that each first electrode iscoupled to a word line through a diode.

[0019] Further embodiments of the invention include methods of varyingscope.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] FIGS. 1A-1D are cross-sectional views of a chalcogenide memoryelement during various processing stages.

[0021] FIGS. 2A-2D are cross-sectional views of a chalcogenide memoryelement during various processing stages in accordance with anembodiment of the invention.

[0022]FIG. 3 is a schematic illustration of one physical vapordeposition apparatus suitable for use with the embodiments of theinvention.

[0023]FIG. 4 is a schematic of a portion of a memory array in accordancewith an embodiment of the invention.

[0024]FIG. 5 is a simplified block diagram of an integrated circuitmemory device in accordance with an embodiment of the invention.

DETAILED DESCRIPTION

[0025] In the following detailed description of the present embodiments,reference is made to the accompanying drawings that form a part hereof,and in which is shown by way of illustration specific embodiments inwhich the invention may be practiced. These embodiments are described insufficient detail to enable those skilled in the art to practice theinvention, and it is to be understood that other embodiments may beutilized and that process, electrical or mechanical changes may be madewithout departing from the scope of the present invention. The termswafer or substrate used in the following description include any basesemiconductor structure. Examples include silicon-on-sapphire (SOS)technology, silicon-on-insulator (SOI) technology, thin film transistor(TFI) technology, doped and undoped semiconductors, epitaxial layers ofa silicon supported by a base semiconductor structure, as well as othersemiconductor structures well known to one skilled in the art.Furthermore, when reference is made to a wafer or substrate in thefollowing description, previous process steps may have been utilized toform regions/junctions in the base semiconductor structure, and theterms wafer and substrate include the underlying layers containing suchregions/junctions. The following detailed description is, therefore, notto be taken in a limiting sense, and the scope of the present inventionis defined only by the appended claims and equivalents thereof.

[0026] FIGS. 2A-2D depict fabrication of a chalcogenide memory element200 as a portion of an integrated circuit device in accordance with oneembodiment of the invention. FIGS. 2A-2D are cross-sectional views takenduring various processing stages.

[0027] In FIG. 2A, a lower or first electrode 210 is formed on asubstrate (not shown). The first electrode 210 contains conductivematerial. Examples include conductively doped polysilicon, carbon (C),metals, metal alloys, metal silicides, conductive metal nitrides andconductive metal oxides. The first electrode 210 may further containmore than one conductive material. For example, the first electrode 210may contain a layer of carbon overlying a layer of molybdenum (Mo) or alayer of tungsten (W) overlying a layer of titanium nitride (TiN). Inaddition, the first electrode 210 may include one or more adhesion orbarrier layers adjacent underlying or overlying layers. Any adhesion orbarrier layer should preferably be conductive as to not interfere withprogramming of the chalcogenide memory element 200. For one embodiment,the first electrode 210 contains silver. For a further embodiment, thefirst electrode 210 is a layer of silver.

[0028] The first electrode 210 is preferably formed using a physicalvapor deposition (PVD) process. Examples include vacuum or thermalevaporation, electron-beam evaporation and sputtering techniques wellknown in the art. In a PVD process, a source or target containing thematerial to be deposited is evaporated and may include ionization ofsome or all of the vaporized target material. The vaporized and/orionized species impinging on the substrate can then deposit on thesubstrate. PVD processes are preferred for their general ability to formlayers of high purity, limited only by the purity of the source ortarget used in the PVD process. However, other deposition techniques maybe used, such as a chemical vapor deposition (CVD) process in whichvaporized chemical precursors are adsorbed on the substrate surface andreacted to form the first electrode 210.

[0029] For one embodiment, the first electrode 210 has a thickness ofapproximately 500-1000 Å. For a further embodiment, the first electrode210 has a thickness of approximately 700 Å.

[0030] Following formation of the first electrode 210, a chalcogenidelayer 215 is formed on the first electrode 210. As with the firstelectrode 210, the chalcogenide layer 215 is preferably formed using aPVD process, but may be formed using other deposition techniques. Forone embodiment, the chalcogenide layer 215 contains a chalcogenidematerial containing one or more Group VIB elements of the traditionalIUPAC version of the periodic table, i.e., oxygen (O), sulfur (S),selenium (Se), tellurium (Te) and polonium (Po), and one or more GroupsIVB and VB elements of the traditional IUPAC version of the periodictable, i.e., carbon (C), silicon (Si), germanium (Ge), tin (Sn), lead(Pb), nitrogen (N), phosphorus (P), arsenic (As), antimony (Sb) andbismuth (Bi). More preferably, the chalcogenide layer 215 contains achalcogenide material containing a combination of selenium and/ortellurium with germanium and/or antimony. For one embodiment, thechalcogenide layer 215 contains a germanium selenite material (GeSe orGeSe₂).

[0031] For one embodiment, the chalcogenide layer 215 has a thickness ofapproximately 300-700 Å. For a further embodiment, the chalcogenidelayer 215 has a thickness of approximately 500 Å.

[0032] As shown in FIG. 2B, the chalcogenide layer 215 is doped withmetal 240 using a sputtering process to produce a doped chalcogenidelayer 230. The doped chalcogenide layer 230 is doped to a desired dopinglevel. For one embodiment, the desired doping level produces a dopedchalcogenide layer 230 saturated with the metal 240. For anotherembodiment, the desired doping level produces an oversaturated dopedchalcogenide layer 230. For yet another embodiment, the desired dopinglevel is approximately 15-30 wt % of the metal 240 in the dopedchalcogenide layer 230.

[0033] One example of an apparatus for performing sputtering may includean ENDURA® system commercially available from Applied Materials, SantaClara, Calif., USA. The plasma generated in such equipment will emit aUV component, thus providing photon-induced diffusion during thesputtering process.

[0034]FIG. 3 is a schematic illustration of one PVD apparatus 310suitable for use with the embodiments of the invention. Those familiarwith PVD apparatus will recognize that it is a simplified schematic andthat typical PVD apparatus may contain additional or alternatecomponents.

[0035] A conductive pedestal 314 containing substrate 312 is located ina deposition chamber 316. The pedestal 314 is connected to a DC powersource 324. A gas inlet 318 is provided for introduction of componentgases into the chamber 316. The component gases make up the plasma 322.The component gases are generally fed to the deposition chamber 316continuously during the operation of the apparatus 310. As used herein,component gases do not include any vaporized target material createdduring the sputter process.

[0036] A sputter target 326 connected to a DC power source 328 islocated in the chamber 316. The target 326 may be a plate formed of thematerial to be sputtered. Examples of materials to be sputtered in thedoping of the chalcogenide layer 215 include high-diffusion metals suchas copper, silver, gold and aluminum. Excess or spent gases are drawnfrom the deposition chamber 316 through a vent 329 by a vacuum pump (notshown).

[0037] In the magnetron configuration, magnets 327 aid in thedevelopment of the plasma 322. The plasma 322 is formed by theapplication of a bias across the target 326 as a cathode and thesubstrate 312 as an anode. Magnets 327 are often placed behind thetarget 326.

[0038] In order to increase the UV component emitted by the plasma, lowmolecular weight noble gases are added to the plasma. In particular, theplasma is formed at least in part using neon (Ne) and/or helium (He).The plasma may further contain other component gases. One example isargon (Ar), which is commonly used in sputtering processes. Whileargon's spectrum has a UV component as well, its relative intensity isrelatively low compared to that of neon or helium, thus resulting inlower rates of metal diffusion. For one embodiment, the plasma usedduring the doping process is generated from feed gas consistingessentially of neon. For another embodiment, the plasma used during thedoping process contains helium. For yet another embodiment, the plasmaused during the doping process contains at least argon and neon. Theplasma could also be generated from feed gas consisting essentially ofhelium for its increased UV component, but such use can lead toundesirable reductions in sputtering efficiency. Use of lower atomicweight gases can result in much higher operating pressures thantraditional PVD processes, e.g., 30-300 mTorr.

[0039] By adjusting the volume percentages of the gases used ingenerating the plasma, a plasma can be generated having an averageatomic weight anywhere between the lowest atomic weight of the gases andthe highest atomic weight of the gases. In this manner, a plasma can becreated having an average atomic weight sufficient to facilitate adesired sputtering efficiency. Sputtering efficiency generally refers tothe number of target atoms ejected per incident ion, typically in therange of about 0.5-1.5. Sputtering efficiency largely determines therate of sputter implantation or deposition. Sputtering efficiencydepends on a number of factors, including the direction of incidentions, target material, mass of bombarding ions, the energy of thebombarding ions, dose, crystal state and surface binding energy.

[0040] It is noted that where more than two gases make up the plasma,multiple combinations of these gases can produce the same average atomicweight. For example, a mixture of 5% argon, 78% neon and 17% helium byvolume will have approximately the same average atomic weight as amixture of 10% argon, 67% neon and 23% helium by volume.

[0041] By adjusting the volume percentages of the gases in the plasma, aplasma also can be generated having a UV component that is a compositeof the spectra of the individual gases and having a relative intensitygenerally between that of the lowest relative intensity of the gases inthe plasma and that of the highest relative intensity of the gases inthe plasma. In this manner, a plasma can be created having a relativeintensity of its composite UV component sufficient to produce a desiredlevel of photon-induced diffusion of the sputtered metal. It is notedthat where more than two gases make up the plasma, multiple combinationsof these gases can emit UV components having the same relativeintensity.

[0042] In view of the above, it is possible to choose a plasma having adesired relative intensity of its emitted UV component and a desiredaverage atomic weight through the selection of two or more componentgases and their relative volume percentages. However, it is recognizedthat these values, i.e., the desired relative intensity and the desiredaverage atomic weight, may be mutually exclusive. In other words,attaining one value may require a compromise on the other. One method ofcompromise would be to determine the combinations of component gasesproducing a plasma having the desired relative intensity and then tochoose one of these combinations of the component gases having anaverage atomic weight near the desired atomic weight. Another methodwould be to determine the combinations of component gases producing aplasma having the desired average atomic weight and then to choose oneof these combinations of the component gases having a relative intensityof its UV component near the desired relative intensity.

[0043] The UV components of differing plasmas may have differingspectra, but the same relative intensity. Because the spectrum can alsoaffect diffusion rates, it may be desirable to produce a specificemitted spectrum in a resulting plasma. Accordingly, for one embodiment,a mixture of component gases is chosen to produce a desired spectrum ofthe resulting plasma. For a further embodiment, a mixture of componentgases is chosen to produce a desired spectrum of the resulting plasmahaving a higher level of visible components than a plasma consisting ofneon. For another embodiment, a mixture of component gases capable ofproducing a desired spectrum in a resulting plasma is chosen to producea target sputter efficiency. In general, the component gases of theplasma used in the sputtering process for doping of the chalcogenidelayer 215 are selected to produce desired diffusion and sputteringrates.

[0044] As an example of how the plasma composition affects diffusion, anexperiment was undertaken to sputter silver onto germanium selenideusing different plasmas, but otherwise comparable processing conditions.Using a plasma generated from feed gas consisting essentially of neon,approximately 501.6 Å of silver were sputtered onto approximately 503 Åof germanium selenide (GeSe). It is presumed that approximately 300 Å ofthe silver diffused into the germanium selenide layer. In contrast,using a plasma generated from feed gas consisting essentially of argon,and sputtering approximately 468.0 Å of silver onto approximately 503 Åof germanium selenide (GeSe), approximately 336.3 Å of silver weredetected on the surface of the germanium selenide. Thus, for argon, itis presumed that only approximately 131.7 Å of the silver diffused intothe germanium selenide layer.

[0045] Returning to FIG. 2C, a top or second electrode 250 is formed onthe doped chalcogenide layer 230. The second electrode 250 generallyfollows the same guidelines as the first electrode 210. Accordingly, thesecond electrode 250 contains conductive material. Examples includeconductively doped polysilicon, carbon, metals (including refractorymetals), metal alloys, metal silicides, conductive metal nitrides andconductive metal oxides. The second electrode 250 may further containmore than one conductive material. In addition, the second electrode 250may include one or more adhesion or barrier layers adjacent underlyingor overlying layers. Any adhesion or barrier layer should preferably beconductive as to not interfere with programming of the chalcogenidememory element 200. For one embodiment, the second electrode 250contains silver. For a further embodiment, the second electrode 250 is alayer of silver.

[0046] The second electrode 250 is preferably formed using a PVDprocess, but may be formed by other methods such as CVD techniques. Thesecond electrode 250 is more preferably formed using the same PVDapparatus and target as used during the doping of the chalcogenide layer215. In this manner, the second electrode 250 may be formed in situ withthe doping process, thus further reducing risks of contamination ordamage associated with transport of the semiconductor substrate.Accordingly, for one embodiment, the second electrode 250 is formed bysputtering metal 245 onto the doped chalcogenide layer 230.

[0047] For one embodiment, the second electrode 250 has a thickness ofapproximately 800-1200 Å. For a further embodiment, the second electrode250 has a thickness of approximately 1000 Å.

[0048] For one embodiment, the component gases used during doping of thechalcogenide layer 215 are evacuated from the deposition chamber 316prior to formation of the second electrode 250. For such an embodiment,a new plasma 322 is formed with the new component gases for thedeposition of the second electrode 250. For example, doping of thechalcogenide layer 215 can be performed using a plasma 322 generatedusing a feed gas consisting essentially of neon. The deposition chamber316 is evacuated after the desired doping level is attained.Subsequently, formation of the second electrode can be performed using aplasma 322 generated using a feed gas consisting essentially of argon.Alternatively or additionally, the second plasma 322 may containnitrogen or oxygen to form conductive metal nitrides or metal oxides,respectively.

[0049] Alternatively, the component gas feed composition could bechanged without an evacuation of the deposition chamber 316. Forexample, doping of the chalcogenide layer 215 can be performed using acomponent gas and plasma 322 having a first composition, e.g.,consisting essentially of neon. As the desired doping level isapproached, the component gas feed could be changed to the secondcomposition, e.g., consisting essentially of argon. For this example,the concentration of argon in the plasma 322 will thus graduallyincrease as argon is fed to the deposition chamber 316 and mixed gasesare drawn off. As the composition of the plasma 322 changes, driving toa higher average atomic weight and/or a lower UV component, the dynamicswould shift away from diffusion and toward deposition. To decrease therate of change in the composition of the plasma 322, the component gasfeed composition could be changed gradually instead of making a stepchange.

[0050] For another embodiment, the processing described with referenceto FIGS. 2B and 2C could be combined using a single composition forplasma 322. For such an embodiment, the component gases are chosen suchthat a desired combination of diffusion and deposition occurs. The rateof diffusion should be high enough relative to the rate of depositionthat sufficient doping occurs before the second electrode 250 becomesthick enough to block further diffusion of metal into the dopedchalcogenide layer 230.

[0051]FIG. 2D shows the chalcogenide memory element 200 upon formationof the second electrode 250. The chalcogenide memory element 200 has adoped chalcogenide layer interposed between the first electrode 210 andthe second electrode 250. The chalcogenide memory element 200 can beused to form a chalcogenide memory cell where the state of the dopedchalcogenide layer 230 is indicative of the data value stored by thememory cell.

[0052]FIG. 4 is a schematic showing a portion of a memory array 400containing chalcogenide memory elements 200 as described herein. Thememory array 400 includes a number of memory cells 405 arrangedgenerally in rows and columns. Typical memory arrays 400 containmillions of these memory cells 405. Each memory cell 405 includes achalcogenide memory element 200 coupled between a first conductive line,such as word line 410, and a diode 415. The diode 415 is further coupledbetween a second conductive line, such as bit line 420, and thechalcogenide memory element 200. Alternatively, the diode 415 could becoupled between the first conductive line and the chalcogenide memoryelement 200. The diode 415 serves as the access device to the memorycell 300. A grouping of memory cells 300 coupled to the same word line410 are typically referred to as a row of memory cells. Likewise, agrouping of memory cells 300 coupled to the same bit line 420 aretypically referred to as a column of memory cells.

[0053]FIG. 5 is a simplified block diagram of an integrated circuitmemory device 500 in accordance with an embodiment of the invention. Thememory device 500 is a non-volatile memory device containingchalcogenide memory elements in accordance with the invention. Thememory device 500 includes an array of memory cells 502 including thenon-volatile chalcogenide memory elements. The memory array 502 isarranged in a plurality of addressable banks. In one embodiment, thememory contains four memory banks 504, 506, 508 and 510. Each memorybank contains addressable rows and columns of memory cells.

[0054] The data stored in the memory array 502 can be accessed usingexternally provided location addresses received by address register 512via address signal connections 528. The addresses are decoded using bankdecode logic 516 to select a target memory bank. The addresses are alsodecoded using row decode circuitry 514 to select the target rows. Theaddresses are further decoded using column decode circuitry 518 toselect one or more target columns.

[0055] Data is input and output through I/O circuit 520 via dataconnections 530. I/O circuit 528 includes data output registers, outputdrivers and output buffers. Command execution logic 522 is provided tocontrol the basic operations of the memory device 500 in response tocontrol signals received via control signal connections 526. A statemachine 524 may also be provided to control specific operationsperformed on the memory array and cells. The command execution logic 522and/or state machine 524 can be generally referred to as controlcircuitry to control read, write, erase and other memory operations. Thedata connections 530 are typically used for bi-directional datacommunication. The memory can be coupled to an external processor 550for operation or testing.

[0056] It will be appreciated by those skilled in the art thatadditional circuitry and control signals can be provided, and that thememory device of FIG. 5 has been simplified to help focus on theinvention. It will be understood that the above description of a memorydevice is intended to provide a general understanding of the memory andis not a complete description of all the elements and features of atypical memory device.

[0057] As recognized by those skilled in the art, memory devices of thetype described herein are generally fabricated as an integrated circuitcontaining a variety of semiconductor devices. The integrated circuit issupported by a substrate. Integrated circuits are typically repeatedmultiple times on each substrate. The substrate is further processed toseparate the integrated circuits into dies as is well known in the art.

[0058] The foregoing figures were used to aid the understanding of theaccompanying text. However, the figures are not drawn to scale andrelative sizing of individual features and layers are not necessarilyindicative of the relative dimensions of such individual features orlayers in application. Accordingly, the drawings are not to be used fordimensional characterization.

[0059] Although dimensional characteristics were provided herein forinformation purposes, it is recognized that there is a continuing driveto reduce integrated circuit device dimensions for increased performanceand reduced fabrication costs. In addition, the concepts describedherein are not fundamentally limited by absolute dimensions.Accordingly, improvements in fabrication and sensing technologies areexpected to facilitate reduced dimensional characteristics of thechalcogenide memory elements described herein, particularly as theyrelate to layer thickness.

Conclusion

[0060] Methods have been described for forming metal-doped chalcogenidelayers and devices containing such doped chalcogenide layers. Themethods include using a plasma to induce diffusion of metal into achalcogenide layer concurrently with metal deposition. The plasmacontains at least one noble gas of low atomic weight, such as neon orhelium. The plasma has a sputter yield sufficient to sputter a metaltarget and a UV component of its emitted spectrum sufficient to inducediffusion of the sputtered metal into the chalcogenide layer. Using suchmethods, a conductive layer can be formed on the doped chalcogenidelayer in situ. In integrated circuit devices, such as non-volatilechalcogenide memory devices, doping of a chalcogenide layer concurrentlywith metal deposition and formation of a conductive layer in situ withthe doping of the chalcogenide layer reduces contamination concerns andphysical damage resulting from moving the device substrate from tool totool, thus facilitating improved device reliability.

[0061] Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat any arrangement that is calculated to achieve the same purpose maybe substituted for the specific embodiments shown. Many adaptations ofthe invention will be apparent to those of ordinary skill in the art.Accordingly, this application is intended to cover any adaptations orvariations of the invention. It is manifestly intended that thisinvention be limited only by the following claims and equivalentsthereof.

What is claimed is:
 1. A method of forming a doped chalcogenide layer,comprising: sputtering metal onto a layer of chalcogenide material inthe presence of a plasma containing at least one component gas selectedfrom the group consisting of neon and helium.
 2. The method of claim 1,wherein the chalcogenide material is a germanium selenide material. 3.The method of claim 1, wherein the plasma further contains a noble gashaving an atomic weight higher than an atomic weight of neon.
 4. Themethod of claim 3, wherein the noble gas having an atomic weight higherthan the atomic weight of neon is argon.
 5. The method of claim 1,wherein the plasma is generated from a feed gas consisting essentiallyof neon.
 6. The method of claim 1, wherein the metal is selected fromthe group consisting of aluminum, copper, silver and gold.
 7. The methodof claim 1, wherein the chalcogenide material contains at least oneelement selected from the group consisting of oxygen, sulfur, selenium,tellurium and polonium, and at least one element selected from the groupconsisting of carbon, silicon, germanium, tin, lead, nitrogen,phosphorus, arsenic, antimony and bismuth.
 8. The method of claim 1,wherein the chalcogenide material contains at least one element selectedfrom the group consisting of selenium and tellurium, and at least oneelement selected from the group consisting of germanium and antimony. 9.A method of forming a doped chalcogenide layer, comprising: forming alayer of chalcogenide material; sputtering particles from a metal targetin the presence of a plasma containing at least neon; depositing thesputtered particles on the layer of chalcogenide material; and diffusingthe sputtered particles into the layer of chalcogenide material.
 10. Themethod of claim 9, wherein the metal target contains a metal selectedfrom the group consisting of aluminum, copper, silver and gold.
 11. Themethod of claim 9, wherein diffusing the sputtered particles into thelayer of chalcogenide material occurs concurrently with sputtering theparticles from the metal target.
 12. The method of claim 9, wherein theplasma is generated from a feed gas consisting essentially of neon. 13.The method of claim 9, wherein the plasma further contains helium. 14.The method of claim 9, wherein the plasma further contains argon. 15.The method of claim 9, wherein the plasma further contains at least onenoble gas having an atomic weight different from an atomic weight ofneon.
 16. The method of claim 9, further comprising: selecting componentgases for the plasma comprising neon and at least one noble gas otherthan neon, each component gas having an atomic weight; and adjustingvolume percentages of the component gases to generate an average atomicweight sufficient to facilitate a desired sputtering efficiency.
 17. Themethod of claim 9, further comprising: selecting component gases for theplasma comprising neon and at least one noble gas other than neon; andadjusting volume percentages of the component gases to generate a plasmahaving a desired emitted spectrum.
 18. The method of claim 17, whereinadjusting volume percentages of the component gases to generate a plasmahaving a desired emitted spectrum further comprises adjusting volumepercentages of the component gases to generate a plasma having anemitted spectrum that has a higher level of visible components than aplasma containing neon alone.
 19. The method of claim 9, furthercomprising: selecting component gases for the plasma comprising neon andat least one noble gas other than neon, each component gas having a UVcomponent of its emitted spectrum; and adjusting volume percentages ofthe component gases to generate a plasma having a desired relativeintensity of a UV component of an emitted spectrum of the plasma. 20.The method of claim 19, wherein the desired relative intensity of the UVcomponent of the emitted spectrum of the plasma is a relative intensitysufficient to produce a desired level of diffusion of the sputteredparticles into the layer of chalcogenide material.
 21. The method ofclaim 9, further comprising: selecting component gases for the plasmacomprising neon and at least one noble gas other than neon, eachcomponent gas having an atomic weight and a UV component of its emittedspectrum; determining at least two combinations of the component gasesproducing a plasma having a relative intensity of a UV component of anemitted spectrum of the plasma sufficient to produce a desired level ofdiffusion of the sputtered particles into the layer of chalcogenidematerial; and choosing one of the combinations of the component gaseshaving an average atomic weight nearest a desired average atomic weight.22. The method of claim 9, further comprising: selecting component gasesfor the plasma comprising neon and at least one noble gas other thanneon, each component gas having an atomic weight and a UV component ofits emitted spectrum; determining at least two combinations of thecomponent gases producing a plasma having an average atomic weightsufficient to facilitate a desired sputtering efficiency; and choosingone of the combinations of the component gases producing a plasma havinga desired relative intensity of a UV component of an emitted spectrum ofthe plasma.
 23. A method of forming a doped chalcogenide layer,comprising: forming a layer of chalcogenide material; and sputteringmetal onto the layer of chalcogenide material and diffusing thesputtered metal into the layer of chalcogenide material using a plasmacontaining at least two noble gases, wherein a composition of the plasmais chosen to have an average atomic weight sufficient to produce adesired sputtering efficiency.
 24. The method of claim 23, wherein eachnoble gas is selected from the group consisting of helium, neon andargon.
 25. A method of forming a doped chalcogenide layer, comprising:forming a layer of chalcogenide material; and sputtering metal atomsonto the layer of chalcogenide material and diffusing the metal atomsinto the layer of chalcogenide material using a plasma containing atleast two noble gases, wherein a composition of the plasma is chosen tohave a desired relative intensity of a UV component of an emittedspectrum of the plasma.
 26. A method of forming a doped chalcogenidelayer, comprising: forming a layer of chalcogenide material; andsputtering metal onto the layer of chalcogenide material and diffusingthe sputtered metal into the layer of chalcogenide material using aplasma containing at least two noble gases, wherein a composition of theplasma is chosen to have a desired emitted spectrum of the plasma.
 27. Amethod of forming a chalcogenide memory element having a firstelectrode, a second electrode, and a doped chalcogenide layer interposedbetween the first electrode and the second electrode, the methodcomprising: forming a chalcogenide layer on the first electrode;sputtering metal onto the chalcogenide layer using a first plasmacontaining at least one component gas selected from the group consistingof neon and helium, thereby forming the doped chalcogenide layer,wherein the first plasma emits a UV component sufficient to inducediffusion of the sputtered metal into the chalcogenide layer; andsputtering metal onto the doped chalcogenide layer using a second plasmacontaining at least one component gas having an atomic weight higherthan an atomic weight of neon, thereby forming the second electrode. 28.The method of claim 27, wherein the at least one component gas having anatomic weight higher than an atomic weight of neon is argon.
 29. Themethod of claim 27, wherein forming a chalcogenide layer furthercomprises forming a layer of germanium selenide material, whereinsputtering metal onto the chalcogenide layer using the first plasmafurther comprises sputtering silver, and wherein sputtering metal ontothe doped chalcogenide layer using the second plasma also comprisessputtering silver.
 30. The method of claim 27, wherein the first plasmaand the second plasma are the same plasma.
 31. The method of claim 27,wherein the second electrode has a different work function (φ_(m)) thanthe first electrode.
 32. A method of forming a chalcogenide memoryelement having a first electrode, a second electrode, and a dopedchalcogenide layer interposed between the first electrode and the secondelectrode, the method comprising: forming a chalcogenide layer on thefirst electrode; sputtering metal onto the chalcogenide layer using afirst plasma containing at least one component gas selected from thegroup consisting of neon and helium, thereby forming the dopedchalcogenide layer; and sputtering metal onto the doped chalcogenidelayer using a second plasma containing at least argon, thereby formingthe second electrode.
 33. A method of forming a chalcogenide memoryelement having a first electrode, a second electrode, and a dopedchalcogenide layer interposed between the first electrode and the secondelectrode, the method comprising: forming a chalcogenide layer on thefirst electrode; sputtering metal onto the chalcogenide layer using aplasma containing at least one component gas selected from the groupconsisting of neon and helium, thereby forming the doped chalcogenidelayer; and sputtering metal onto the doped chalcogenide layer using theplasma, thereby forming the second electrode.
 34. A method of forming achalcogenide memory element having a first electrode, a secondelectrode, and a doped chalcogenide layer interposed between the firstelectrode and the second electrode, the method comprising: forming achalcogenide layer on the first electrode; sputtering metal onto thechalcogenide layer using a plasma initially generated from feed gascontaining at least one component gas selected from the group consistingof neon and helium, thereby forming the doped chalcogenide layer;increasing an average atomic weight of the feed gas used to generate theplasma; and sputtering metal onto the doped chalcogenide layer using theplasma generated from the feed gas having the increased average atomicweight, thereby forming the second electrode.
 35. The method of claim34, wherein increasing an average atomic weight of the feed gas used togenerate the plasma further comprises evacuating the feed gas afterforming the doped chalcogenide layer and generating the plasma used forforming the second electrode using the feed gas having the higheraverage atomic weight.
 36. The method of claim 34, wherein increasing anaverage atomic weight of the plasma further comprises modifying feedrates of component gases into the plasma while sputtering metal.
 37. Amethod of forming a chalcogenide memory element having a firstelectrode, a second electrode, and a doped chalcogenide layer interposedbetween the first electrode and the second electrode, the methodcomprising: forming a chalcogenide layer on the first electrode;sputtering metal onto the chalcogenide layer using a first plasma in adeposition chamber to form the doped chalcogenide layer, wherein thefirst plasma is generated using at least one component gas selected fromthe group consisting of neon and helium; and sputtering metal onto thedoped chalcogenide layer using a second plasma in the deposition chamberto form the second electrode, wherein the second plasma is generatedusing at least one component gas having an atomic weight higher than anatomic weight of neon.
 38. The method of claim 37, wherein the at leastone component gas used in generating the first plasma consistsessentially of neon.
 39. The method of claim 37, wherein the at leastone component gas used in generating the second plasma consistsessentially of argon.
 40. The method of claim 39, wherein the secondplasma is generated using at least argon.
 41. The method of claim 37,wherein sputtering metal onto the doped chalcogenide layer to form thesecond electrode is performed in situ with sputtering metal onto thechalcogenide layer to form the doped chalcogenide layer.
 42. The methodof claim 37, wherein sputtering metal onto the chalcogenide layer toform the doped chalcogenide layer further comprises sputtering from ametal target and wherein sputtering metal onto the doped chalcogenidelayer to form the second electrode further comprises sputtering from thesame metal target.
 43. The method of claim 42, wherein the metal targetis a silver target and the chalcogenide layer contains a germaniumselenide material.
 44. The method of claim 37, wherein the first plasmaand the second plasma each contain at least one component gas selectedfrom the group consisting of neon and helium and at least one componentgas having an atomic weight higher than an atomic weight of neon. 45.The method of claim 44, wherein the first plasma and the second plasmahave the same composition.
 46. A method of forming a chalcogenide memoryelement having a first electrode, a second electrode, and a dopedchalcogenide layer interposed between the first electrode and the secondelectrode, the method comprising: forming a chalcogenide layer on thefirst electrode; sputtering silver onto the chalcogenide layer using afirst plasma generated from a feed gas consisting essentially of neon,thereby forming the doped chalcogenide layer; and sputtering a metalonto the doped chalcogenide layer using a second plasma generated from afeed gas consisting essentially of argon, thereby forming the secondelectrode, wherein the second electrode has a different work function(φ_(m)) than the first electrode.
 47. A method of forming a chalcogenidememory element having a first electrode, a second electrode, and a dopedchalcogenide layer interposed between the first electrode and the secondelectrode, the method comprising: forming a chalcogenide layer on thefirst electrode; sputtering silver onto the chalcogenide layer using afirst plasma consisting essentially of neon, thereby forming the dopedchalcogenide layer; and sputtering silver onto the doped chalcogenidelayer using a second plasma consisting essentially of argon, therebyforming the second electrode.
 48. The method of claim 47, wherein thechalcogenide layer is a germanium selenide material.
 49. A method offorming a non-volatile memory device, comprising: forming word lines;forming first electrodes coupled to the word lines, wherein each wordline is coupled to more than one first electrode; forming a chalcogenidelayer on each first electrode; sputtering metal onto each chalcogenidelayer using a first plasma containing at least one component gasselected from the group consisting of neon and helium, thereby formingdoped chalcogenide layers; sputtering metal onto each doped chalcogenidelayer using a second plasma containing at least one component gas havingan atomic weight higher than an atomic weight of neon, thereby formingsecond electrodes; and forming bit lines coupled to the secondelectrodes, wherein each bit line is coupled to more than one secondelectrode.
 50. The method of claim 49, further comprising: formingdiodes, wherein each diode is formed at a location selected from thegroup consisting of interposed between a second electrode and a bitline, such that each second electrode is coupled to a bit line through adiode, and interposed between a first electrode and a word line, suchthat each first electrode is coupled to a word line through a diode. 51.A method of forming a non-volatile memory device, comprising: formingword lines; forming first electrodes coupled to the word lines, whereineach word line is coupled to more than one first electrode; forming achalcogenide layer on each first electrode; sputtering metal onto eachchalcogenide layer using a first plasma containing at least onecomponent gas selected from the group consisting of neon and helium,thereby forming doped chalcogenide layers; sputtering metal onto eachdoped chalcogenide layer using a second plasma containing at least onecomponent gas having an atomic weight higher than an atomic weight ofneon, thereby forming second electrodes; forming a diode coupled to eachsecond electrode; and forming bit lines coupled to the diodes, whereineach bit line is coupled to more than one diode.
 52. A method of forminga non-volatile memory device, comprising: forming word lines; formingdiodes coupled to the word lines, wherein each word line is coupled tomore than one diode; forming a first electrode coupled to each diode;forming a chalcogenide layer on each first electrode; sputtering metalonto each chalcogenide layer using a first plasma containing at leastone component gas selected from the group consisting of neon and helium,thereby forming doped chalcogenide layers; sputtering metal onto eachdoped chalcogenide layer using a second plasma containing at least onecomponent gas having an atomic weight higher than an atomic weight ofneon, thereby forming second electrodes; forming a diode coupled to eachsecond electrode; and forming bit lines coupled to the secondelectrodes, wherein each bit line is coupled to more than one secondelectrode.
 53. A method of forming a non-volatile memory device,comprising: forming word lines; forming first electrodes coupled to theword lines, wherein each word line is coupled to more than one firstelectrode; forming a chalcogenide layer on each first electrode;sputtering silver onto each chalcogenide layer using a first plasmaconsisting essentially of neon, thereby forming doped chalcogenidelayers; sputtering a metal onto each doped chalcogenide layer using asecond plasma consisting essentially of argon, thereby forming secondelectrodes, wherein the metal has a different work function (φ_(m)) thanthe first electrodes; and forming bit lines coupled to the secondelectrodes, wherein each bit line is coupled to more than one secondelectrode.
 54. A method of forming a non-volatile memory device,comprising: forming word lines; forming first electrodes coupled to theword lines, wherein each word line is coupled to more than one firstelectrode; forming a chalcogenide layer on each first electrode;sputtering silver onto each chalcogenide layer using a first plasmaconsisting essentially of neon, thereby forming doped chalcogenidelayers; sputtering silver onto each doped chalcogenide layer using asecond plasma consisting essentially of argon, thereby forming secondelectrodes; and forming bit lines coupled to the second electrodes,wherein each bit line is coupled to more than one second electrode. 55.The method of claim 54, further comprising: forming diodes, wherein eachdiode is formed at a location selected from the group consisting ofinterposed between a second electrode and a bit line, such that eachsecond electrode is coupled to a bit line through a diode, andinterposed between a first electrode and a word line, such that eachfirst electrode is coupled to a word line through a diode.